In order to meet applicable governmental emission standards, an automobile must be equipped with a device to remove noxious components from the engine exhaust. Many types of converters have been employed in the attempt to remove these noxious components. Early versions of catalytic converters were designed to oxidize carbon monoxide (CO) and various unburned hydrocarbons (HC). To accomplish this, oxygen must be introduced into the exhaust gas. In view of more stringent environmental standards, newer catalytic converters are required to reduce the oxides of nitrogen (NO.sub.x) as well. That reaction, however, requires a scarcity of oxygen so that the NO.sub.x will react with the CO in the presence of a suitable catalyst to form nitrogen (N.sub.2) and CO.sub.2 generally in accordance with the following reaction: EQU 2CO+2NO.fwdarw.N.sub.2 +2CO.sub.2 +Heat
Many presently available catalytic converters provide for a two-stage process wherein two separate catalyst beds are utilized: the oxides of nitrogen being reduced via the first catalyst bed, and, following the injection of air, the carbon monoxide and hydrocarbons being oxidized via the second catalyst bed. Such a device is described in Hardison U.S. Pat. No. 3,701,823, in which a first and a second catalyst bed are maintained in a heat exchange relationship, air being injected into the exhaust gas stream between the first and second catalyst bed. These prior art devices require a relatively complicated and expensive construction, including the use of two separate catalyst beds.
It is an object of the present invention to provide a catalytic converter that is capable of reducing the oxides of nitrogen, and oxidizing the carbon monoxide and unburned hydrocarbons in an exhaust gas stream.
It is another object of this invention to provide such a catalytic converter that utilizes only one catalyst bed.
It is a further object of this invention to provide such a catalytic converter that is of simple construction and is economical to manufacture.